An air bag ECU (Electronic Control Unit) develops an air bag by flowing a constant electric current (e.g., an electric current of about 1 Ampere to 2 Amperes) for ignition to a squib when it is judged that a collision, etc. are caused in a vehicle. A constant electric current circuit for this air bag ignition can be constructed by a circuit similar to an overcurrent protecting circuit shown in, for example, JP-A-2005-252968. Concretely, as shown in FIG. 20, the constant electric current circuit is constructed as an IC having transistors T1 to T11, MOSFET M1, constant electric current circuit CC1 and shunt resistor Rs. Resistor RL in this figure equivalently shows electric characteristics of the squib as a load.
When an output electric current Io is flowed to resistor RL through shunt resistor Rs and MOSFET M1, an electric current ratio of transistors T7 and T8 is changed in accordance with a voltage between terminals of shunt resistor Rs. Transistors T9 and T10 constitute a current mirror circuit, and the same electric current as transistor T7 is flowed to this transistor T9. On the other hand, transistor T5 connected in series to transistor T10 outputs a constant electric current. As its result, the gate voltage of MOSFET M1 is controlled on the basis of the voltage between terminals of shunt resistor Rs, and output electric current Io is constantly controlled. A circuit for detecting the electric current by using the shunt resistor is disclosed in JP-A-10-75598 (corresponding to EP 0827266-B1), JP-A-2000-131369 and JP-A-2000-166279 (corresponding to U.S. Pat. No. 6,198,315).
In FIG. 20, when shunt resistor Rs is formed by wiring of aluminum, etc., the resistance value of shunt resistor Rs is dispersed by dispersion of sheet resistance, and the controlled constant electric current value is shifted from a target value. Further, the above constant electric current circuit performs no constant electric current operation if there is no predetermined electric potential difference between the terminals of shunt resistor Rs. Therefore, in an inspecting process after assembly of IC, a load electrically equivalent to the load connected at the real using time is connected, and the operation and the constant electric current value are confirmed. However, in a wafer inspecting process, the inspection is made by making a probe come in contact with a pad on a wafer. Therefore, when the electric current is increased (e.g., when the electric current exceeds several tens milliamperes to several hundreds milliamperes), it becomes difficult to make the inspection.
Thus, it is required for a semiconductor integrated circuit device to have sufficiently controlled electric current value and to make the inspection in the inspecting process before assembly even when a comparatively large electric current is controlled.